Sequence analysis of leukocyte chemoattractant peptides secreted by periovulatory ovine follicles

Cells of the white blood series infiltrate ovarian follicles during the ovulatory process. A segment of the wall of periovulatory ovine follicles was incubated and conditioned media subjected to ultrafiltration. Leukocyte chemoattractant activity of media was measured using a linear under-agarose migration assay. Bioactivity was recovered following filtration through a 3000 molecular weight cut-off membrane. Filtrate was then fractionated by reverse phase high performance liquid chromatography. Peptides recovered from two fractions with significant chemoattractant activity were sequenced. One fraction contained 16 amino acid residues with repeating triplets of Gly-X-Y, where X and Y were often proline and hydroxyproline, respectively. Because this motif is characteristic of alpha collagens, and since thecal collagen is degraded during the mechanics of ovulation, it appears that this chemoattractant is derived from the connective tissue matrix of the follicle. Peptide isolated from the other bioactive chromatographic fraction was 15 amino acids in length, and rich in glycine, but did not contain imino acids. To our knowledge this is the first report of purification of leukocyte chemoattractants of reproductive tissue origin. Resident follicular granulocytes and mononuclear cells are capable of secreting a broad spectrum of potent chemicals that could be involved in the mechanisms of ovulation and luteinization.